National Institute For Materials Science Research Articles

Mechanical Properties of Ultra-Thin Nb3Sn Composite Wires

Flexible Rutherford cables are needed to realize high field superconducting magnets with A15 conductors based on the react-and-wind (R&W) technology. Aiming such an application, ultra-thin A15 composite wires with a diameter of 0.03–0.05 mm have been developed by the National Institute for Materials Science (NIMS). Mechanical properties of such ultra-thin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires were evaluated to determine the cabling parameters and mechanical analysis of twisted cables. Tensile tests were performed at room temperature for 0.05 mm-thick Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires before and after heat treatment for the first time. Basic mechanical parameters such as 0.2% proof strength and fracture strength were evaluated from a stress–strain curve. Young's modulus of such a thin wire was determined from unlading and reloading slopes of a load–stroke curve for the specimens with different gauge lengths. Fracture strain was estimated without using extensometers and strain gauges by correcting for machine deformation. Based on these results, we concluded that a simple technique to measure stress–strain curves for ultra-thin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires was able to be established.

A creep life prediction model of P91 steel coupled with back-propagation artificial neural network (BP-ANN) and θ projection method

In order to predict the long-term creep life of P91 steel, this work proposed a coupled model, combining the error-trained back-propagation artificial neural network (BP-ANN) and an improved θ model. Both the short-term rupture life obtained by creep experiments and the related creep data of National Institute for Materials Science (NIMS) database were used to validate the above model. In this model, creep parameters (temperature, stress) were used as the input and relative error of 5 θ model extrapolations as the output. Then, the prediction errors of BP-ANN method were introduced to correct the 5 θ model extrapolation results to achieve a more accurate prediction. Consequently, the long-term creep life of P91 steel was predicted. It demonstrated that with the proposed model, the prediction capability for long-term creep life of P91 steel with 200,000 h is much better than those of other θ methods, which has a prediction uncertainty less than 5%.

Hydrogen Liquefaction by Active Magnetic Regenerative Refrigeration

The article summarizes the research and development of magnetic refrigeration for hydrogen liquefaction, and the Active Magnetic Regenerative Refrigeration (AMRR) developed by National Institute for Materials Science (NIMS). The NIMS-AMR consists of optimized AMR beds, a superconducting solenoid with correction coils, and a dedicated liquid hydrogen vessel with a liquid level sensor. This article also reports the first successful demonstration of hydrogen liquefaction with the AMRR.

Magnetic Refrigeration System Group, National Institute for Materials Science

Magnetic Refrigeration System Group, National Institute for Materials Science

Gigacycle Fatigue Properties of Wrought Aluminum Alloys

Fatigue data sheets of the National Institute for Materials Science disclose the results of gigacycle fatigue tests conducted on wrought aluminum alloys. The materials tested were hot-rolled plates and extruded round bars of A5083P-O (two heats), A7075-T6 (three heats), and A6061-T6 (three heats). The fatigue testing methods were rotating-bending at 100 Hz, ultrasonic at 20 kHz, and uniaxial at 100 Hz. The rotating-bending fatigue tests were conducted for 3 years to reach 1010 cycles. The ultrasonic and uniaxial fatigue tests were also conducted at high stress ratios. This study analyzed the fatigue life data, clarifying frequency effects, presence or absence of fatigue limits, and stress ratio effects. The three types of fatigue tests revealed equivalent results, meaning that frequency effects and stress gradient effects were negligible in the wrought aluminum alloys. Frequency effects were visible in several cast aluminum alloys owing to the influence of humidity, but the wrought aluminum alloys were observed to be insensitive to humidity. Many specimens were fractured at >107 cycles, whereas the degradation of fatigue strength after 107 cycles was very small in A5083P-O but large in A7075-T6 and A6061-T6. A5083P-O revealed fatigue limits at around 107 cycles. The heat treatment effects determined the presence or absence of fatigue limits because the equivalent tensile strengths between A6061-T6 and A5083P-O excluded the possibility of tensile strength effects. The stress ratio effects on gigacycle fatigue strengths of the wrought aluminum alloys are reasonable and can be estimated in conventional ways.

On material-agnostic fatigue life prediction using Buckingham Pi Theorem

A robust, quantitative analysis is needed to prevent frequent, catastrophic failure of components in powerplants and aircraft, to cite but two examples, due to cyclic loading that could lead to fatigue failure. The model presented in this research will be useful in the reliable design and safe operation of components and equipment. A fatigue life (the dependent variable) prediction model, which employs both stress-based, and stress–strain based criteria is presented that uses the Buckingham Pi Theorem with the experimental parameters influencing fatigue behaviour taken as the independent variables. The validation of the model is done using reliable, frequently used uniaxial fatigue data, culled from the NIMS (National Institute for Materials Science, Tsukuba, Japan) fatigue database on important industrial alloys that experience fatigue loading in service. (No reliable data on such a scale were available to test the validity of this model under multi-axial fatigue loading conditions.) It is demonstrated that the model predicts the experimental results accurately. The accuracy of prediction is examined for every case and compared with that of some other existing methods. Moreover, the potential applicability of this analysis in areas not yet validated is examined.

Better utilization of materials’ compositions for predicting their properties: Material composition visualization network

Owing to the complexity and diversity of advanced high-performance materials, it is challenging to comprehensively understand a material’s composition–process–structure–performance relationship. Data-driven approaches have been regarded as the fourth paradigm of new materials R&D. However, the complexity of constituent elements in many material datasets leads to very sparse compositional features, posing a tremendous challenge to machine learning models. In this study, a data mapping scheme based on fundamental atomic features was used to visualize the chemical composition characteristics mapped into two-dimensional grayscale image data to solve the problem of sparse material composition matrix. Based on this, a material composition visualization network (MCVN) is proposed and applied to predict the mechanical properties of steel and classify amorphous alloy materials. We compared the MCVN to other machine learning methods. The MCVN had an average R2 value improvement of 4% on the four targets in the National Institute for Materials Science’s (NIMS’s) steel dataset, where other models already get an average R2 of 0.92, and it achieved an R2 of 0.835 on the cross-sectional shrinkage target in the Shanghai Research Institute of Materials’(SRIM’s) steel dataset where the other models only had an average R2 of 0.64. For the unbalanced amorphous alloy material dataset, the MCVN improved the average Recall of the small-class crystalline alloy (CRA) from 0.58 to 0.78. The method based on expanding the material chemical composition information is universal and provides a new paradigm for material property prediction.

Visualization of Materials Science Topics in Publications of Institutional Repository using Natural Language Processing

SAMURAI (NIMS 2022), a directory service of the National Institute for Materials Science (NIMS) researchers in Japan was launched in 2009 following the development of NIMS institutional repository (Tanifuji et al. 2019). The concept is to synchronize between profile information of researchers and their publications which are self-archived in the repository system. The SAMURAI was renewed in 2017 with interoperable functions with ORCID. SAMURAI supports various links to not only individual articles and patents, but also to databases such as KAKEN (Database of Grants-in-Aid for Scientific Research by NII). The service has yielded fully identified authors of journal articles from research members of NIMS by implementing a unique ResearcherID. Through this directory, NIMS is promoting materials research, supporting management of its researchers activities, and introducing NIMS researchers and their work to the public. In this work, we present an application to describe each researcher's output topics automatically from the archived research papers in the repository, by implementing materials science specific natural language processing developed in our study (Dieb et al. 2021) that visualizes the research trend of each SAMURAI researchers. The approach can maximize information absorbance for general audience and fully corresponds to open science policy. A list of publications' digital object identifiers (DOIs DOI 2022) for each researcher was constructed from his profile in SAMURAI. (In SAMURAI, the DOIs are stored in a PostgreSQL database). Using the DOI, recent publications were retrieved from NIMS text data mining platform (TDM-PF) in their XML format which were mainly available from 2003. Representative topic terms from their research publications that are related to materials science and engineering were extracted. We utilize term frequency analysis and automatic extraction for materials names to extract these necessary informative terms. Additionally, domain knowledge resources such as dictionaries were used. Data was preprocessed using noise reduction such as removing general English language stop words and physical units filtering. Such words do not have significance on their own. Word cloud approach was used for visualization (Fig. 1). This work brings us an opportunity to apply our NLP experience to mine information from research papers for public knowledge as a step towards data-driven materials science.

Critical Characteristics of Ultrafine Nb3Al Superconducting Wires Under Conduction Cooling Conditions

In recent years, an ultrafine Nb₃Al wires with a diameter of less than 50 &#x03BC;m has been developed by a research group at the National Institute for Materials Science (NIMS) in Japan. Therefore, we are planning to use the developed high performance Nb₃Al wires for superconducting applications operated by cryocooler. In order to design the superconducting applications cooled by cryocooler, it is necessary to measure the temperature and magnetic field dependence of the critical current of Nb₃Al wires under conduction cooling conditions. Single and seven-stranded Nb₃Al wires with different diameters (&#x03D5;67 &#x03BC;m and &#x03D5;81 &#x03BC;m) fabricated by the Jelly-rolled method were prepared. The barrier material of the two samples is the same Nb, but the core materials are Nb (&#x03D5;67 &#x03BC;m) and Ta (&#x03D5;81 &#x03BC;m), respectively. The Cu&#x002F;nonCu ratio of the two samples is 1. In this study, the critical currents of sample wires were measured by a four-probe method with current sweep and constant current, and they were compared to define a reasonable critical current value under conduction cooling. Under conduction cooling, it was confirmed that the critical current measurement by the constant current method was more accurate than the current sweep method.

Ultrathin Magnesium Metal Anode – An Essential Component for High‐Energy‐Density Magnesium Battery Materialization

AbstractInvited for this month's cover picture is the group from National Institute for Materials Science, Japan. The cover picture shows the rechargeable magnesium batteries incorporating ultrathin magnesium metal foils with the energy densities of 72 Wh kg−1 based on the weight of both cathodes and anodes. Read the full text of the article at 10.1002/batt.202200153

Identifying New Classes of High Temperature Superconductors With Convolutional Neural Networks

Applying machine learning to aid the search for high temperature superconductors has recently been a topic of significant interest due to the broad applications of these materials but is challenging due to the lack of a quantitative microscopic model. Here we analyze over 33,000 entries from the Superconducting Materials Database, maintained by the National Institute for Materials Science of Japan, assigning crystal structures to each entry by correlation with Materials project and other structural databases. These augmented inputs are combined with material-specific properties, including critical temperature, to train convolutional neural networks (CNNs) to identify superconductors. Classification models achieve accuracy &amp;gt;95% and regression models trained to predict critical temperature achieve R2 &amp;gt;0.92 and mean absolute error ≈ 5.6 K. A crystal-graph representation whereby an undirected graph encodes atom sites (graph vertices) and their bonding relationships (graph edges), is used to represent materials’ periodic crystal structure to the CNNs. Trained networks are used to search though 130,000 crystal structures in the Materials Project for high temperature superconductor candidates and predict their critical temperature; several materials with model-predicted TC &amp;gt;30 K are proposed, including rediscovery of the recently explored infinite layer nickelates.

Multistep inorganic synthesis and thermal insulation based on 3D THz phononic structure

In order to mitigate climate change, there is a need for new methods and technologies that will help reduce humankind's reliance on fossil fuels and this is something that scientists and researchers are integral to. At the National Institute for Materials Science (NIMS), Japan, Dr Norifusa Satoh is leading a project based on thermal insulation that has the potential to advance energy utilisation principles and techniques. Satoh has been interested in biological systems and how they can help in the development of improved inorganic materials. Currently, he is exploring methods of insulating heat at the same level as electricity. The key focus is 3D periodical structures matching the periodicity with the wavelength of THz phonons, quantised vibrations in thermal transport in materials over room temperature. Because the wavelength of THz phonons is less than 1 nm, to examine 3D THz phononic structures, he attempts to synthesise 3D periodical structures with atomic precision in a multistep manner based on the logic of chemical synthesis. Satoh intends to adapt previously developed methodologies to visualise the thermal resistivity of thermoelectric modules using heat sinks with a thermogram, which will enable him to test and validate his research findings. Ultimately, he hopes the fundamental understanding of THz phonons will contribute to energy savings in myriad ways and help pave the way towards a carbon-free future society.

“Soft Shorts” Hidden in Zinc Metal Anode Research

Qing Li is currently a Ph.D. candidate in the Department of Materials Science and Engineering at City University of Hong Kong, under the supervision of Professor Chunyi Zhi. Her current research mainly focuses on advanced flexible aqueous zinc-ion batteries and the design of advanced metallic anode. Qing obtained her bachelor's degree in engineering from Central South University in 2014 and received her dual master's degree in engineering from Tsinghua University and Hong Kong University of Science and Technology in 2017. She has worked in the battery industry from 2017 to 2019 before joining Prof. Zhi's group. Ao Chen is currently a Ph.D. candidate in the Department of Materials Science and Engineering at City University of Hong Kong, under the supervision of Professor Chunyi Zhi. His research mainly focuses on flexible lithium-ion batteries, high-voltage zinc batteries, and lithium–sulfur batteries. Donghong Wang is currently a Postdoctoral Fellow in the Hong Kong Centre for Cerebro-Cardiovascular Health Engineering under the supervision of Prof. Chunyi Zhi. She received her PhD and master's degree from City University of Hong Kong and University of Science and Technology of China, respectively. Her research mainly focuses on high-performance aqueous multivalence batteries and flexible aqueous multivalence battery devices. Zengxia Pei received his Ph.D. from City University of Hong Kong in 2017. He currently works as an Australian Research Council DECRA Fellow at the University of Sydney. His research focuses on the design and development of nanomaterials for sustainable energy conversion and storage in fields including aqueous batteries/capacitors, electrocatalysis, and functional polyelectrolytes. He was recognized as one of the Australian Research Top Rising Stars in 2019-2021, a JMCA Emerging Investigator in 2021, and a Clarivate Analytics Highly Cited Researcher (cross-field) in 2020 and 2021. Chunyi Zhi obtained B.S. degree in Physics at Shandong University and Ph.D. degree in condensed matter physics at Institute of Physics, Chinese Academy of Sciences. After two years' postdoc at National Institute for Materials Science (NIMS) in Japan, he was promoted to be ICYS researcher, researcher (faculty) and senior researcher (permanent position) in NIMS. Dr. Zhi is now a professor in MSE, City University of Hong Kong. Dr. Zhi has extensive experiences in flexible energy storage, aqueous electrolyte batteries, and zinc ion batteries. He has published more than 400 papers and been granted more than 80 patents.

(Invited) Study of HfO2-Based High-k Gate Insulators for GaN Power Device

Gallium nitride (GaN) high-electron-mobility transistor and vertical GaN devices with metal-oxide-semiconductor (MOS) structure have been widely investigated to suppress leakage currents for applications associated with high power and high frequency [1-3]. Metal oxide (High-k) with a high dielectric constant (k)-value have been employed instead of SiO2 from the viewpoint of increasing the physical thickness [4, 5]. HfO2-based materials including HfO2, HfSiOx and HfAlOx are the candidate materials because of its relatively large bandgap (~6.5 eV) and a high k value (> 13) [6-9]. These films for transistor applications are typically fabricated using atomic layer deposition (ALD) because ALD is compatible with semiconductor fabrication process and has a big advantage of conformal film fabrication on three-dimensional structure. In this study, we report comparison of characteristics among HfO2, HfSiOx and HfAlOx gate insulators of GaN MOS capacitors.Pt-gated n-GaN MOS capacitors with HfO2, HfSiOx and HfAlOx gate insulators were prepared as follows. A single HfO2 layer, (HfO2)m/(SiO2)n and (HfO2)m/(Al2O3)n nanolaminate layers were deposited on n+-GaN/n-GaN epilayer by plasma-enhanced ALD at 300°C. The m/n ratio was kept at 2/1. Next, PDA was carried out at 800°C in N2. HfSiOx and HfAlOx films were formed from (HfO2)m/(SiO2)n and (HfO2)m/(Al2O3)n nanolaminate after PDA, respectively. The thicknesses of these films were ~24 nm. Finally, Pt gate electrode was deposited on gate insulator and Pt/Ti ohmic contact was deposited on the n-GaN substrate.The HfSiOx and HfAlOx films had an amorhous structure while HfO2 film had a polycrystalline structure after PDA at 800°C using transmission electron microscopy and electron diffraction pattern analysis. The HfO2 capacitor exhibited a small breakdown electric field (EBD) value of 2.6 MV/cm, defined at a current density of 1.0 × 101 A/cm2, because leakage currents easily flow along grain boundaries of the polycrystalline structure. On the other hand, the EBD values of the HfSiOx and HfAlOx capacitors increased up to 8.5 MV/cm. From capacitance-voltage measurements, the estimated k values of the HfO2, HfSiOx and HfAlOx films were 17.7, 17.2 and 13.5, respectively, as expected. The flatband voltage hysteresis (620 mV) of the HfO2 capacitor was much larger than those (~10 mV) of the HfSiOx and HfAlOx capacitors, indicating that the number of charge trapping/detrapping sites and frequency responsive defects was significantly decreased in the HfSiOx and HfAlOx capacitors. No frequency dispersion of the HfSiOx and HfAlOx capacitors were observed while the HfO2 capacitor showed a large frequency dispersion. The interface state density (Dit) values at Ec - E = 0.25 eV which estimated using the conductance method of the HfSiOx (~1 × 1011cm-2V-1) and HfAlOx (4.4 × 1011cm-2V-1) capacitors were one magnitude lower than that of the HfO2 capacitor (3.1 × 1012cm-2V-1), indicating that the electrical defects at n-GaN/HfSiOx and n-GaN/HfAlOx interfaces were much less than that of the n-GaN/HfO2 interface.We conclude that the HfSiOx and HfAlOx were the attractive materials as gate insulator because of amorphous structure, higher k, relatively low Dit, and high Ebd.This work was supported by JSPS KAKENHI (Grant No. JP20H02189). A part of this work was also supported by the MEXT “Program for research and development of next-generation semiconductor to realize energy-saving society.” Program Grant Number JPJ005357. The authors wish to thank Dr. A. Ohi, Dr. N. Ikeda, and the members of the nanofabrication group of the National Institute for Materials Science for their support during this study.[1] M. Kodama et al., Appl. Phys. Express 1, 021104 (2008).[2] Z. Yatabe et al., J. Phys. D: Appl. Phys. 49, 393001 (2016).[3] T. Oka et al., Appl. Phys. Express 8, 054101 (2015).[4] T. Hashizume et al., Appl. Phys. Express 11, 124102 (2018).[5] T. Kikuta et al, J. Vac. Sci. Technol. A 35, 01B122 (2017).[6] T. Nabatame et al., Appl. Phys. Express 12, 011009 (2019).[7] E. Maeda et al., Microelectron. Eng. 216, 111036 (2019).[8] R. Ochi et al., AIP Advances 10, 065215 (2020).[9] S. Miyazaki et al., ECS Trans. 92, 11(2019).

Interfaces and Applications

Interfaces and Applications

Superconducting System Group, National Institute for Materials Science

Superconducting System Group, National Institute for Materials Science

Strategy and Issue for Li-S Batteries with High Energy Density

As an inexpensive, abundantly available, and environmental-friendly material, sulfur has become one of the most promising positive electrode active materials because of its high theoretical specific capacity (1675 mAh g-1). However, lithium sulfur batteries (Li-S Battery) still have some issues for practical application: the electronically insulating nature of sulfur and its discharge products (Li2S/Li2S2); the dissolution and shuttle effect of lithium polysulfides (LiPSs) in the conventional dioxolane/dimethoxyethane (DOL/DME) electrolyte. In addition, excess amounts of electrolyte that overcompensate for its minimum requirement are necessary for achieving a high specific capacity of sulfur, which severely reduces the energy density of the battery. However, only poor charge/discharge behavior could be obtained when the E/S ratios lower than 5 with the conventional DOL/DME electrolyte.1 In order to overcome the above problems, we have proposed sparingly solvating electrolytes made with lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and sulfolane (SL), in which LiPSs have limited solubility to inhibit the LiPS shuttling effect. Moreover, to realize high energy density Li-S batteries, it is essential to reduce the E/S ratio (E/S [μL-electrolyte/mg-sulfur]). Here, we fabricated a pouch cell using the sparingly solvating electrolytes and the cyclability with various E/S ratios was studied.The sparingly solvating electrolytes are [Li(SL)2][TFSA] (Li[TFSA] : SL = 1 : 2) in which a poorly solvating diluent, 1,1,2,2,-tetrafluoroethyl-2,2,3,3,-tetrafluoropropyl ether (HFE), was added at different molar ratios. Sulfur cathodes consisted of sulfur and Ketjen black (KB) at a ratio of 3: 1, which are coated on a carbon-coated aluminum foil with carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR) binders. Pouch cells, which have laminated structures, were prepared using the sulfur cathode, Li metal anode, and Celgard3501 separator. Constant current charge/discharge tests were carried out at cut-off voltage 1.0-3.3 V and at 30 ℃.There were non-negligible differences in electrochemical performances of Li-S batteries between coin cells and pouch cells. Especially, under lean electrolyte conditions (low E/S), only pouch cells gave reasonable results. A high energy density Li-S cell having higher energy density than 300 Wh/kg was successfully demonstrated. Therefore, fabrication of pouch cell is a necessary step to probe the stability of the electrode and to evaluate the electrochemical performances under different low E/S ratios. Fig. 1 shows the capacity retention of Li-S cells with various E/S ratios. Although the initial discharge capacity was almost the same, being independent of E/S ratios. However, the cycle stability significantly deteriorated with decreasing E/S. An internal short circuit due to the dendrite formation also occurred relatively early when E/S < 5. On the other hand, when E/S> 5, a high capacity could be maintained, and an internal short circuit hardly occurred even at the relatively high current density. In pouch cells, the electrode area is generally much larger than that in coin cells. Therefore, the absolute magnitude of current is much higher. As a result, if side reactions between electrolyte and Li anode occur and current density in the cell becomes inhomogeneous, the current concentration in the cell will leads to the dendrite growth. Considering the reduction of E/S is urgent for practical high energy density of Li-S battery, it is necessary to suppress the side reactions and dendrite growth on the lithium anode. By using ab initio molecular dynamics simulations and operando electrochemical mass spectroscopy together with cryo-STEM-EELS techniques, the side reactions between the electrolyte and Li anode were explored. How to reduce the side reactions will be discussed in detail in the presentation.AcknowledgementsThis study was supported by the Advanced Low Carbon Technology Research and Development Program (ALCA) of the Japan Science and Technology Agency (JST). We also appreciate Dr. Keisuke Shinoda for his kind support for Cryo-STEM-EELS measurement at National Institute for Materials Science (NIMS) Battery Research Platform.

Characteristic of Flexible Reram with Al2O3/TiO2 Active Layer By ALD and PDA Process at Low Temperature

1. Introduction The resistive random access memory (ReRAM), which is a nonvolatile memory device, on flexible plastic substrate have been widely investigated for future wearable device. The flexible ReRAM based on metal-insulator-metal (MIM) structure is generally fabricated at relatively low temperature (~250°C) from the viewpoint of heat resistance of plastics. Numerous active layers, including Al2O3-TiO2, Al2O3-HfO2, and Al2O3-Ta2O5 bilayers have been studied in a aim of improving resistive swithing reliability. In our previous paper, we found that Pt/Al2O3/TiO2/Pt capacitor fabricated on Si substrate by atomic layer deposition (ALD) and a post-deposition annealing (PDA) process at 200°C, exhibited bipolar resistive swithing charactreistics with a high resistive state (HRS) and a low resisitive state (LRS) in a small switching voltage of ±0.8V.In this paper, we fabricated Pt/Al2O3/TiO2/Pt capacitors on polyimide (PI) substrate by ALD and PDA process at 200°C and examined reliabilities of resistive swithing properties under tensile stress. 2. Experiment MIM capacitors with Al2O3/TiO2 active layer were prepared as follows. First, a 200-nm-thick SiO2 layer as gas barrier was deposited on PI substrate. Pt bottom electrode (BE-Pt) was deposited on PI/SiO2 layer by DC sputtering. A 5-nm-thick Al2O3 layer was deposited on BE-Pt by ALD at 200°C using Al(CH3)3 precursor and H2O gas and subsquently PDA was carried out at 200°C in N2. Next, a 60-nm-thick TiO2 layer was deposited on Al2O3 layer by ALD at same temperature, using Ti[N(CH3)2]4 precursor and H2O gas and PDA was performed at 200°C in O2. Finally, Pt top electrode (TE-Pt) was fabricated on the TiO2 layer by DC sputtering. The area of the TE-Pt was approximately 1.5 ´ 10-4 cm-2. 3. Results and discussion Each of Al2O3 and TiO2 layer of the flexible Pt/Al2O3/TiO2/Pt capacitor on PI had an amorphous structure because no spotty electron diffraction pattern was observed by TEM and EDS measurement. There were no severe chemical reactions in any of the layers.Fig 1 shows the J-V characterestics of the flexible Pt/Al2O3/TiO2/Pt capacitor. The first forming process was performed to occur the irreversible breakdown of the Al2O3 layer when applied voltage was increased to + 7V. The second forming process was the creation of a TiO2-x layer due to the oxygen vacancies (Vo) near the TE-Pt and TiO2 layer when voltage was applied -3V. The set process (switching from the HRS to the LRS) caused at an applied voltage of about +1V and the reset process (switching from the LRS to the HRS) occurred at about -1V. These set and reset processes appeared due to the Vo transfer into TiO2 layer when voltage applied in positive and negative directions. Stable bipolar switching properies between the HRS and the LRS was obtained until the number of swithing cycles of 20. We also observed resistive swithing characteristics of about 2 orders of magnitude between the HRS and the LRS under tensile stress condition. 4. Summary We conclude that flexible Pt/Al2O3/TiO2/Pt capacitors on PI exhibited stable bipolar switching characteristics of the HRS and LRS after two forming steps of breaking Al2O3 layer and creating a TiO2-x layer due to the Vo. Furthermore, a similar resistive switching property was obtained regardless of tensile stress. Acknowledgement This work was partially supported by JSPS KAKENHI Grant Number of JP20H02189. The authors thank all staff members of the Nanofabrication group of the National Institute for Materials Science (NIMS) for their support. Figure 1

Emerging Nanomaterials for Light‐Driven Reactions: Past, Present, and Future

Emerging Nanomaterials for Light‐Driven Reactions: Past, Present, and Future

Realtime Up-sampling Noise Filter: Paradigm Shift for Data Acquisition

Journal Article Realtime Up-sampling Noise Filter: Paradigm Shift for Data Acquisition Get access Akimitsu Ishizuka, Akimitsu Ishizuka HREM Research Inc., Higashimatsuyama, Saitama, Japan Search for other works by this author on: Oxford Academic Google Scholar Koji Kimoto, Koji Kimoto National Institute for Materials Science, Tsukuba, Ibaraki, Japan Search for other works by this author on: Oxford Academic Google Scholar Kazuo Ishizuka Kazuo Ishizuka HREM Research Inc., Higashimatsuyama, Saitama, Japan Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 26, Issue S2, 1 August 2020, Pages 1936–1938, https://doi.org/10.1017/S143192762001987X Published: 01 August 2020